Cardiac Conduction System

1. Cardiac Conduction System

2. (1) Conduction System of Heart • Conduction System = Heart Beat & Pumping • Cardiac Contractions = Unconscious • Autonomic Nervous System  decrease or increase heart rate depending on circumstance

3. (2) Depolarization of the Heart • Generate Action Potential & Depolarization: • Atria  Ventricles • Depolarization Path: • SA Node  AV Node • Atria Contract • (Delay)  AV Bundle • Ventricles Contract (Blood ejected out of arteries, leaving heart)

4. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html

5. (3) Nodes & Bundles • Sinoatrial Node (SA Node) • Right atrium • Starts each heart beat & sets rate • “Pacemaker” • Atrioventricular Node (AV Node) = Left atrium • AV Bundle = • Bundle Branches (along septum) • Purkinje Fibers (along entire muscular wall of heart)

7. (4) Cardiac Cycle • Diastole = Relax • Blood passively filling atria • Systole = Contract • Ventricles contract • Blood Ejected out of heart

9. (5) Diastole • Ventricles relax 2. Semilunar valves closed 3. Ventricular Presure < Atrial Pressure • AV valves open • Ventricles fill with blood 4. Atria contract and force blood remaining in chambers into ventricles

11. (6) Systole • Pressure increases in ventricles • Filled with blood • AV valves close 3. Pressure in ventricles > Arteries leaving heart • Semilunar valves open • Blood rushes out of ventricles 4. Atria are relaxed and begin to fill back up

13. (7) Heart Beat • You hear something like “lub” “dup” • “lub” = closing of AV valves • During ventricular systole • “dup” = closing of semilunar valves • During early diastole • You should NOT hear blood flow • You’ll hear it if flow is interrupted by blockage http://www.csulb.edu/org/college/bme/respiratory_sounds/heart.wav

14. (8) Cardiac Output • Cardiac Output • Amount of blood pumped out by each ventricle / 1 minute • Cardiac Output = Heart Rate x Stroke Volume • CO = (HR)(SV) • Stroke Volume • Volume of blood pumped out by ventricle • Increase of SV = Increase of ventricular force + contraction • Average Stroke Volume = 0.2L • Average Cardiac Output = 15L/min

15. (9) Starling’s Law • Starling’s Law of the Heart: • Degree of cardiac muscle extension before contraction • Increase Extension = Stronger Contraction • Degree of Extension  result of percent filling of ventricles